// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_SPDY_SPDY_FRAME_READER_H_
#define NET_SPDY_SPDY_FRAME_READER_H_

#include <stddef.h>
#include <stdint.h>

#include "base/strings/string_piece.h"
#include "net/base/net_export.h"

namespace net {

// Used for reading SPDY frames. Though there isn't really anything terribly
// SPDY-specific here, it's a helper class that's useful when doing SPDY
// framing.
//
// To use, simply construct a SpdyFramerReader using the underlying buffer that
// you'd like to read fields from, then call one of the Read*() methods to
// actually do some reading.
//
// This class keeps an internal iterator to keep track of what's already been
// read and each successive Read*() call automatically increments said iterator
// on success. On failure, internal state of the SpdyFrameReader should not be
// trusted and it is up to the caller to throw away the failed instance and
// handle the error as appropriate. None of the Read*() methods should ever be
// called after failure, as they will also fail immediately.
class NET_EXPORT_PRIVATE SpdyFrameReader {
public:
    // Caller must provide an underlying buffer to work on.
    SpdyFrameReader(const char* data, const size_t len);

    // Empty destructor.
    ~SpdyFrameReader() { }

    // Reads an 8-bit unsigned integer into the given output parameter.
    // Forwards the internal iterator on success.
    // Returns true on success, false otherwise.
    bool ReadUInt8(uint8_t* result);

    // Reads a 16-bit unsigned integer into the given output parameter.
    // Forwards the internal iterator on success.
    // Returns true on success, false otherwise.
    bool ReadUInt16(uint16_t* result);

    // Reads a 32-bit unsigned integer into the given output parameter.
    // Forwards the internal iterator on success.
    // Returns true on success, false otherwise.
    bool ReadUInt32(uint32_t* result);

    // Reads a 64-bit unsigned integer into the given output parameter.
    // Forwards the internal iterator on success.
    // Returns true on success, false otherwise.
    bool ReadUInt64(uint64_t* result);

    // Reads a 31-bit unsigned integer into the given output parameter. This is
    // equivalent to ReadUInt32() above except that the highest-order bit is
    // discarded.
    // Forwards the internal iterator (by 4B) on success.
    // Returns true on success, false otherwise.
    bool ReadUInt31(uint32_t* result);

    // Reads a 24-bit unsigned integer into the given output parameter.
    // Forwards the internal iterator (by 3B) on success.
    // Returns true on success, false otherwise.
    bool ReadUInt24(uint32_t* result);

    // Reads a string prefixed with 16-bit length into the given output parameter.
    //
    // NOTE: Does not copy but rather references strings in the underlying buffer.
    // This should be kept in mind when handling memory management!
    //
    // Forwards the internal iterator on success.
    // Returns true on success, false otherwise.
    bool ReadStringPiece16(base::StringPiece* result);

    // Reads a string prefixed with 32-bit length into the given output parameter.
    //
    // NOTE: Does not copy but rather references strings in the underlying buffer.
    // This should be kept in mind when handling memory management!
    //
    // Forwards the internal iterator on success.
    // Returns true on success, false otherwise.
    bool ReadStringPiece32(base::StringPiece* result);

    // Reads a given number of bytes into the given buffer. The buffer
    // must be of adequate size.
    // Forwards the internal iterator on success.
    // Returns true on success, false otherwise.
    bool ReadBytes(void* result, size_t size);

    // Seeks a given number of bytes into the buffer from the current offset.
    // Equivelant to an empty read.
    // Forwards the internal iterator.
    // Returns true on success, false otherwise.
    bool Seek(size_t size);

    // Rewinds this reader to the beginning of the frame.
    void Rewind() { ofs_ = 0; }

    // Returns true if the entirety of the underlying buffer has been read via
    // Read*() calls.
    bool IsDoneReading() const;

    // Returns the number of bytes that have been consumed by the reader so far.
    size_t GetBytesConsumed() const { return ofs_; }

private:
    // Returns true if the underlying buffer has enough room to read the given
    // amount of bytes.
    bool CanRead(size_t bytes) const;

    // To be called when a read fails for any reason.
    void OnFailure();

    // The data buffer that we're reading from.
    const char* data_;

    // The length of the data buffer that we're reading from.
    const size_t len_;

    // The location of the next read from our data buffer.
    size_t ofs_;
};

} // namespace net

#endif // NET_SPDY_SPDY_FRAME_READER_H_
